Preheat the oven to 400 degrees F.

Grab a small baking dish, a piece of foil and another larger baking dish that the smaller baking dish fits in.

Pour the sweetened condensed milk into the smaller baking dish and cover it with foil.

Place the smaller baking dish in the larger baking dish and fill halfway with water.

Transfer to the oven to bake for 1 hour to 1 hour and 15 minutes.

Remove it from the oven and allow it to stand for about 15 minutes.

Remove the foil from the baking dish and remove it from the water bath.

Discard the cinnamon stick and pour the dulce de leche/manjar blanco into a glass or stainless steel bowl.

Whisk it until it's smooth.

To the medium bowl, whisk together the all-purpose flour, sifted corn starch, powdered sugar and salt. Set aside.

To the bowl of a stand-up mixer, add the butter and vanilla paste or extract. Beat until smooth.

Next, add the egg yolk and mix just until incorporated.

Add all of the flour mixture and slowly mix it together until combined, about 1 minute.

Scoop the dough out of the bowl and form it into a ball.

Place it in the center of a sheet of plastic wrap and press it into about a 2-inch round.

Wrap it tightly in plastic wrap and transfer to the fridge to chill for about 1 hour.

Preheat the oven to 350 degrees F.

Transfer the dough to the center of a sheet of parchment. Place a sheet of parchment on top and roll it out slowly.

Roll it out until it's about ½ to ¼-inch thick.

Using a 3-inch cookie cutter, stamp out cookies.

Transfer the cookies to a parchment-lined baking sheet, spacing them about 2-inches apart.

Transfer to the fridge to chill for about 10 minutes.

Score the tops of the cookies with the tines of a fork.

Transfer to the oven to bake for about 11 to 13 minutes.

Allow to cool on the baking sheets until room temperature.

When the cookies have cooled, flip half of the cookies on their opposite side.

Transfer the manjar blanco to a piping bag with a piping tip attached.

Pipe a round of manjar blanco on all of the cookies facing their opposite sides.

Top each of the cookies with another cookie and lightly press it down.

Roll the sides in the sifted powdered sugar.

Store in an air-tight container or bag for up to 3 to 5 days.